IS : 1919 - 1982
(Reaffirmed 2010)

Edition 2.3 (2004-10)

Indian Standard
SPECIFICATION FOR SODIUM HYDROSULPHITE

( First Revision )
( Incorporating Amendment Nos. 1, 2 & 3 ) UDC 661.833.542

© BIS 2004 BUREAU OF INDIAN STANDARDS MANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG NEW DELHI 110002 Price Group 6

IS : 1919 - 1982

Indian Standard
SPECIFICATION FOR SODIUM HYDROSULPHITE

( First Revision )
Inorganic Chemicals (Misc) Sectional Committee, CDC 3
Chairman
DR. M. S. VAIDYA

Members
SHRI P.V. S. RAO ( Alternate to
SHRI S. K. BASU

Representing The Dharamsi Morarji Chemical Co Ltd, Bombay

DR. M. S. Vaidya )

SHRI D. S. CHOWDHURY ( Alternate ) DR. R. M. BHATNAGAR SHRI B. N. BHATTACHARYYA SHRI S. N. BHATTACHARYA SHRI S. GANAPATHY (Alternate) SHRI S. S. HONAVAR

Directorate General of Supplies and Disposals, New Delhi The Fertilizer (P & D) India Ltd, Sindri Geological Survey of India, Calcutta Tata Chemicals Ltd, Bombay Italab Private Ltd, Bombay General of Technical Development, New Delhi

SHRI M. V. DABHOLKAR (Alternate II) SHRI J. S. MATHARU Directorate

SHRI J. C. DEY (Alternate I)

SHRI R. C. BHATTACHARYYA (Alternate) SHRI S. V. NAYAK J. K. Chemicals Ltd, Thane SHRI P. A. MENON (Alternate) SHRI J. K. PATWA Sarabhai M. Chemicals, Vadodara SHRI H. H. KAVARANA (Alternate) SHRI A. K. RAO D. C. M. Chemical Works, New Delhi SHRI B. K. VAHI (Alternate) SHRI B. K. SACHAR Ministry of Defence (R & D) SHRI A. D. GUPTA (Alternate) SHRI C. R. SANTHANAKRISHNAN Travancore Chemical & Mfg Co Ltd, Mettur SHRI K. V. MANI (Alternate) DR. H. S. SARKAR The Durgapur Projects Ltd, Durgapur SHRI P. SATYANARAYAN Development Commissioner, Small DR. E. R. SAXENA DR. MOD. ZAFAR JAMIL (Alternate) SHRI H. C. SHAH Golden

Dam

Scale Industries, New Delhi Regional Research Laboratory (CSIR), Hyderabad Chemicals Pvt Ltd, Bombay (Continued on Page 2)

SHRI S. GANAPATHY (Alternate)

© BIS 2004 BUREAU OF INDIAN STANDARDS This publication is protected under the Indian Copyright Act (XIV of 1957) and reproduction in whole or in part by any means except with written permission of the publisher shall be deemed to be an infringement of copyright under the said Act.

IS : 1919 - 1982
( Continued from page 1 ) Members
SHRI Y. V. SHETTY DR. V. SRINIVASAN SHRI P. MANSUKHANI (Alternate) DR. SURJIT SINGH SHRI N. C. THAKKAR DR. HARI BHAGWAN,

Representing Indian Oil Corporation Ltd (Refineries and Pipelines Division), New Delhi Glaxo Laboratories (India) Ltd, Bombay Ministry of Defence (DGI) Indian Chemical Manufacturers' Association, Calcutta Director General, BIS ( Ex-Officio Member) Secretary

DR. A. K. SEN (Alternate)

Director (Chem)

Assistant Director (Chem), ISI

SHRI M. BAKSHI GUPTA

Auxiliary Chemical Subcommittee, CDC 3:18
Convener
DR. M. S. VAIDYA

The Dharamsi Morarji Chemical Co Ltd, Bombay

Members SHRI R. S. VYAS (Alternate to Dr. M. S. Vaidya)
SHRI S. V. AVADHOOT SHRI J. T. VORA (Alternate) SHRI A. T. BRAHMBHATT SHRI P. M. SARAIYA (Alternate) SHRI R. K. GANDHI SHRI N. K. GUHA SHRI D. P. SINGH (Alternate) SHRI M. M. KAUL SHRI M. A. KOTIBHASKAR SHRI U. V. KUNIKULLAYA

Deepak Nitrite Ltd, Bombay Kalali Chemicals Ltd, Vadodara Tata Chemicals Ltd, Bombay Development Commissioner, Small Industries, New Delhi Khosla Metal Powders Ltd, Pune Phoenix Chemical Works Pvt Ltd, Bombay Tamil Nadu Chromates & Chemicals Ltd, Madras J. K. Chemicals Ltd, Thane The Travancore-Cochin Chemicals Udyogamandal Golden Chemicals Pvt Ltd, Bombay The Millowners' Association, Bombay Waldies Ltd, Calcutta Ltd, Scale

SHRI S. P. KHOSLA (Alternate)

SHRI M. A. CHUNEKAR (Alternate)

SHRI S. V. NAYAK SHRI P. A. MENON( Alternate) SHRI G. P. PILLAI SHRI C. N. G. NAIR (Alternate) SHRI H. C. SHAH SHRI S. GANAPATHY (Alternate I ) SHRI Y. M. RAWAL (Alternate II) SHRI K. M. SHAH SHRI D. V. WITTENBAKER

SHRI M. N. KINI (Alternate)

2

IS : 1919 - 1982

Indian Standard
SPECIFICATION FOR SODIUM HYDROSULPHITE

( First Revision )
0. F O R E W O R D 0.1 This Indian Standard (First Revision) was adopted by the Indian Standards Institution on 24 February 1982, after the draft finalized by the Inorganic Chemicals (Misc) Sectional Committee had been approved by the Chemical Division Council. 0.2 Sodium hydrosulphite, also known as sodium dithionite is used as reducing and bleaching agent in textiles, dyestuffs, leather, paper, pulp and other industries. It is also used for bleaching purposes, in jaggery and sugar manufacture and as a food preservative and in pharmaceutical preparations. This standard, however, does not cover the pharmaceutical grade of the material. 0.3 The use of hydrosulphite in jaggery or any other foodstuff industries is in such small quantities that even if the hydrosulphite contains a few ppm of mercury and even assuming all this finds its way to the food product, the same would not be contaminated to the extent as to make it injurious to health. However, it is felt essential to stipulate a maximum limit for mercury to take care of any abnormal increase of its carry-over in the product. In this standard a realistic limit of 0.1 parts per million has been specified so that the manufacturers can aim at achieving production of the material within this limit with the existing procedures and equipment. 0.4 Until recently sodium hydrosulphite was being manufactured by the zinc process and amalgam process; the material is now being produced in the country employing sodium formate process also. This standard issued in 1961, is therefore being revised to cover specifications of the material for all the three processes. 0.5 This edition 2.3 incorporates Amendment No. 1 (April 1986), Amendment No. 2 (July 1994) and Amendment No. 3 (October 2004). Side bar indicates modification of the text as the result of incorporation of the amendments. 0.6 For the purpose of deciding whether a particular requirement of this standard is complied with, the final value, observed or calculated, 3

IS : 1919 - 1982 expressing the result of a test or analysis, shall be rounded off in accordance with IS : 2-1960*. The number of significant places retained in the rounded off value should be the same as that of the specified value in this standard. 1. SCOPE 1.1 This standard prescribes the requirements and the methods of sampling and test for sodium hydrosulphite (Na2S2O4). 2. GRADES 2.1 There shall be two grades of the material, namely: Grade 1 -- for dyestuff industry; and Grade 2 -- for textiles, jaggery, etc, and as a bleaching agent. 3. REQUIREMENTS 3.1 Description -- The material shall be in the form of granular powder, white to light grey in colour. The material dissolves in water at room temperature, giving initially a clear solution which on standing may become slightly turbid. 3.2 The material shall also comply with the requirements given in Table 1 when tested according to the methods prescribed in Appendix A. Reference to the relevant clauses of Appendix A is given in col 4 of the table. 4. KEEPING QUALITY 4.1 The material, when stored unopened in original air-tight containers, shall continue to satisfy the requirements given in Table 1 for at least three months from the date of packing. 5. PACKING AND MARKING 5.1 Packing -- The material shall be packed in air-tight mild steel or fibreboard drums with polyethylene liner. Each container shall be securely closed. 5.2 Marking -- Each container shall bear legibly and indelibly the following information: a) Name and grade of the material; b) Name of the manufacturer and his recognized trade-mark, if any;
*Rules for rounding off numerical values ( revised ).

4

IS : 1919 - 1982 c) Gross and net mass; d) Date of packing; e) Batch number; and f) The cautional label 'FLAMMABLE ! KEEP IN COOL AND DRY PLACE' and the relevant symbol for labelling dangerous goods [see I S : 1260 (Part 1)-1973*].
TABLE 1 REQUIREMENTS FOR SODIUM HYDROSULPHITE ( Clauses 3.2 and 4.1 ) NO.
SL CHARACTERISTIC REQUIREMENT

Grade 1 (3) 88.0 0.9 to 1.3 20 -- 10 0.6 To pass the test To pass the test

Grade 2 (4) 84.0 0.9 to 1.3 20 0.1 10 0.6 To pass the test To pass the test

METHOD OF TEST, REF TO CL NO. IN APPENDIX A

(1) (2) i) Sodium hydrosulphite (as Na2S2O4), percent by mass, Min ii) Bulk density, kg/1 iii) Zinc (as Zn), mg/kg, Max iv) Mercury (as Hg), mg/kg, Max v) Heavy metals (as Pb), mg/kg, Max vi) Sodium formate (as HCOONa), percent by mass, Max vii) Methanol (as CH3OH) viii) Sodium oxalate (as Na2C2O4)

(5) A-2 A-3 A-4 A-5 A-6 A-7 A-8 A-9

5.2.1 The containers may also be marked with the ISI Certification Mark.
NOTE -- The use of the ISI Certification Mark is governed by the provisions of the Indian Standards Institution (Certification Marks) Act and the Rules and Regulations made thereunder. The ISI Mark on products covered by an Indian Standard conveys the assurance that they have been produced to comply with the requirements of that standard under a well-defined system of inspection, testing and quality control which is devised and supervised by ISI and operated by the producer. ISI marked products are also continuously checked by ISI for conformity to that standard as a further safeguard. Details of conditions under which a licence for the use of the ISI Certification Mark may be granted to manufacturers or processors may be obtained from the Indian Standards Institution. *Pictorial markings for handling and labelling of goods : Part I Dangerous goods (first revision).

5

IS : 1919 - 1982 6. SAMPLING 6.1 The method of drawing representative samples of the material, number of tests to be performed and the methods of finding out the criteria for conformity of the material to the requirements of this specification shall be as prescribed in Appendix B.

( Clause 3.2 and Table 1 ) METHODS OF TEST A-1. QUALITY OF REAGENTS A-1.1 Unless specified otherwise, pure chemicals and distilled water ( see IS : 1070-1977* ) shall be employed in tests.
NOTE -- 'Pure chemicals' shall mean chemicals that do not contain impurities which affect the results of analysis.

APPENDIX A

A-2. SODIUM HYDROSULPHITE A-2.0 Outline of the Method -- Sodium hydrosulphite is treated with excess of formaldehyde to yield bisulphite formaldehyde and sulphoxylate formaldehyde, the latter being determined by titration with iodine. Na 2 S 2 O 4 + 2CH2O + 4H2O = NaHSO3.CH2O.H2O + NaHSO2. CH2O.2H2O NaHSO2.CH2O.2H2O + 41 = NaHSO4 + CH2O + 4HI A-2.1 Reagents A-2.1.1 Formaldehyde -- 37 percent ( v/v ). (Commercial 'formalin'). When formalin is acidic, add 0.1 N sodium hydroxide solution to neutralize it to pH 7. A-2.1.2 Phenolphthalein Indicator Solution -- Dissolve 1 g of the material in 100 ml of 90 percent rectified spirit. A-2.1.3 Starch Indicator Solution -- Mix well 1 g of starch and 10 ml of iced water. Add gradually the solution, with stirring, into 200 ml hot water and boil the contents till the solution becomes semi-transparent. Let stand to cool and use the supernatent liquid.
*Specification for water for general laboratory use ( second revision ). 6

IS : 1919 - 1982 A-2.1.4 Standard Iodine Solution -- 0.1 N. Dissolve about 40 g of potassium iodide in about 2.5 ml of water. Add about 13 g of iodine, dissolve and filter through a filter paper. Add water through the filter paper to make about 1 litre. Put the solution in a brown bottle and agitate. Keep it in a dark place. When using, filter again, and determine the factor of the solution as given below. A-2.1.4.1 Take 25 ml of the solution and titrate with 0.1 N sodium thiosulphate (see A-2.1.5) solution using starch as indicator. Calculate the factor as follows:

where N1 = normality of iodine, V = volume in ml of sodium thiosulphate solution, and N2 = normality of sodium thiosulphate solution. A-2.1.5 Standard Sodium Thiosulphate Solution -- 0.1 N. Dissolve 26 g of sodium thiosulphate and about 0.2 g of the anhydrous sodium carbonate in 500 ml of water. Dissolve and make up the volume to 1 litre in a one-litre flask. Add about 10 ml of isoamyl alcohol and keep the solution in a stoppered bottle for two days. A-2.1.5.1 Weigh accurately 1.226 g of potassium dichromate which has been dried for 2 hours at 120 ± 2° C and then cooled in a sulphuric acid desiccator, dissolve in water and make up to 250 ml in a volumetric flask. Take an aliquot of 25 ml in a 500 ml conical flask, add 15 ml of concentrated hydrochloric acid, cool and then add 15 ml of 10 percent potassium iodide solution. Dilute and titrate the liberated iodine against standard thiosulphate solution ( see A-2.1.5) using starch as indicator. Calculate this normality of standard sodium thiosulphate as follows:

where N = normality of standard sodium thiosulphate, and V = volume in ml of sodium thiosulphate salt solution used in the titration. A-2.1.6 Mixed Solution -- Take 50 ml of formaldehyde solution ( see A-2.1.1 ) and add 50 ml of water and 10 ml of 0.1 N sodium hydroxide solution and 15 drops of phenolphthalein indicator solution. 7

IS : 1919 - 1982 A-2.2 Procedure A-2.2.1 Preparation of the Sample Solution -- Weigh accurately about 4 g of the sample in a 1 000 ml volumetric flask with a glass stopper. Dissolve it in 25 ml of the mixed solution. Make up to the mark with water. A-2.2.2 Pipette about 25 ml of the sample solution ( see A 2.2.1 ) in a conical flask. Add 0.1 N hydrochloric acid until the red colour of the phenolphthalein disappears. Add 15 ml of one percent acetic acid solution and titrate with iodine solution using starch as an indicator. The end point is the persistance of purple colour for 5 seconds on addition of one drop of the iodine solution. A 2.3 Calculation Sodium hydrosulphite, percent by mass = where N1 = normality of standard iodine solution, V2 = volume in ml of iodine solution, and M = mass in g of the material taken for test.
NOTE -- 17.4 is the factor for 0.1 N Iodine Solution.

A-3. BULK DENSITY A-3.1 Apparatus A-3.1.1 Assembly of apparatus is shown in Fig. 1. The base of the measuring cylinder A shall be ground flat and the empty measuring cylinder A together with the rubber bung shall weigh 250 ± 5 g. It shall be accurately calibrated to 250 ml with an error of less than one millilitre. The distance between zero and 250 ml graduation on the measuring cylinder A shall be not less than 220 mm and not more than 240 mm. The distance between the flat ground part of the base of the measuring cylinder A and the rubber base pad B, when the measuring cylinder A is raised to the full height, shall be 25 ± 2 mm. A-3.1.2 The rubber base pad B shall have a shore hardness of 42 to 50. A-3.1.3 Pans of the balance shall be at least 10 cm in diameter and the balance shall be sensitive to less than 0.1 g. A-3.2 Procedure -- Fold a piece of black glazed paper (25 cm × 25 cm) with two parallel creases to form a channel 12.5 mm down the middle of the paper. Transfer 50 g of the material on to the glazed paper. Pick up the paper and foam it into a chute. Allow it to lie between the thumb and fingers on the palm of the hard and introduce it into the
8

IS : 1919 - 1982 cylinder, which should be held at 45°C to the vertical. Slip the powder gently and smoothly into the measuring cylinder without knocking or squeezing. Assemble the apparatus as shown in Fig. 1. With the thumb and four fingers of one hand, gently grasp the upper part of the cylinder, and within one second, lift it as far as 25 mm ( see Fig. 1 ). Do not jerk the cylinder by knocking it against the upper stop. At the start of the next second, release the cylinder smoothly. Continue lifting and dropping until 300 complete drops have been given. Once every two seconds, a gentle twist of about 10° should be given to the cylinder. As soon as 300 drops have been completed, raise the cylinder to eye level and read the volume of the material.

All dimensions in millimetres. FIG. 1 APPARATUS FOR THE DETERMINATION OF BULK DENSITY

A-3.3 Calculation Bulk density, kg/1 = where M = mass in g of the material taken for the test, and V = final volume in ml of the material.

9

IS : 1919 - 1982 A 4. DETERMINATION OF ZINC A-4.0 Test qualitatively for zinc with the same solution as in quantitative estimation, if found positive, then only the quantitative test may be carried out. A-4.1 Apparatus A-4.1.1 Colorimeter A-4.2 Reagents A-4.2.1 Standard Zinc Solution -- Dissolve 100 mg of zinc powder in slight excess of dilute hydrochloric acid (1 : 1). Dilute to 1 000 ml with water in a volumetric flask. Dilute 10 ml of this solution to 100 ml. One millilitre of this solution contains of 10 g of zinc. A-4.2.2 Sodium Ascorbate A-4.2.3 Potassium Cyanide Solution -- Dissolve 1.00 g of potassium cyanide in 50 ml of water and dilute to 100 ml. The solution is stable for about 60 days. CAUTION: 'POTASSIUM CYANIDE IS POISON. HANDLE IT WITH CARE' A-4.2.4 Buffer Solution ( pH 9.0 ) -- Dissolve 40 g of sodium hydroxide in 500 ml of water and dilute to 1 000 ml. Dilute 213 ml of this solution to about 600 ml with water. Dissolve .37.8 g of potassium chloride and 31.0 g of boric acid in the solution and'dilute to one litre. A-4.2.5 Zincon Solution -- Dissolve 130 mg of powdered 2-carboxy2'-hydroxy-5'-sulphoformazyl benzene (zincon) in 100 ml of methyl alcohol. Let the solution stand overnight or use a magnetic stirrer in a closed flask to complete dissolution. A-4.2.6 Chloral Hydrate -- Dissolve 10 g of chloral hydrate in 50 ml of water and dilute to 100 ml, filter, if necessary. A-4.2.7 Concentrated Hydrochloric Acid -- conforming to IS : 265-1976*. A-4.2.8 Sodium Hydroxide Solution -- 6 N. A-4.3 Procedure A-4.3.1 Weigh accurately about 5 g of the-material and transfer into a one-litre and one-necked round bottom flask with a long vertical condenser (preferably a condenser in which cold water circulation is through coiled pipes) along with 200 ml of water and 5 to 10 ml of
*Specification for hydrochloric acid (second revision). 10

IS : 1919 - 1982 concentrated hydrochloric acid, boil and reflux for 2 to 3 hours till all the sulphur dioxide gas is expelled. After refluxing is over, cool, wash down the sides of the condenser and sides of the flask and make up to 1 000 ml, filter, if insoluble residue is present. A-4.3.2 Transfer 0.0 ml, 0.5 ml, 1.0 ml, 2 ml, 3 ml, 4 ml, 5 ml, and 6 ml quantities of standard zinc solution to provide 0, 5, 10, 20, 30, 40, 50 and 60 g of zinc to 50-ml volumetric flasks. Bring each volume to 10 ml by adding water. To each flask, add in sequence (mixing thoroughly) 0.5 g of sodium ascorbate, 1.0 ml of potassium cyanide solution, 5.0 ml of buffer solution, 3.0 ml of zincon solution and 3.0 ml of chloral hydrate solution; note the time and mix well. Transfer the solution to absorption cell and measure the absorbance at 620 nm exactly after 5 minutes of adding chloral hydrate solution in a photometer. Use the treated blank (0.0 ml solution of standard zinc) as the reference solution for initial balancing of the colorimeter. Draw a graph of absorbance against concentration (g of zinc). A-4.3.3 Take 10 ml of the prepared solution in a 50 ml volumetric flask (see A-4.3). Add 0.5 gm of sodium ascorbate, 1.0 ml of potassium cyanide solution, 5.0 ml of Buffer solution, 3.0 ml of zincon solution; and 3.0 ml of chloral hydrate solution; note the time and mix well. Transfer the solution to absorbance cell and measure the absorbance at 620 nm exactly after 5 minutes of adding chloral hydrate solution in a photo-meter. From the measurement of absorbance, find the concentration from the graph. A-4.4 Calculation Zinc, mg/kg = where X = concentration in g of zinc, and M = mass in g of the material taken for the test. A-5. DETERMINATION OF MERCURY A-5.1 Apparatus A-5.1.1 Cold Vapour Atomic Absorptlometer -- ECIL mercury analyser. A-5.2 Reagents A-5.2.1 Standard Mercury Solution -- Dissolve 1.36 g of mercury chloride in concentrated nitric acid, add 10 ml of potassium dichromate solution (one percent, m/v) and make up to one litre with water (solution A). One ml of this solution is equivalent to 1 mg of mercury. Dilute this solution as under. 11

IS : 1919 - 1982 A-5.2.1.1 Take one ml of solution A in a 1-litre volumetric flask, add 6 ml of dilute nitric acid (two percent v/v) and 3 ml of potassium dichromate solution (one percent, m/v) and make up to the mark. One ml of the solution is equivalent to 1 g of mercury (solution B). A-5.2.1.2 Take 10 ml of solution B in a 100 ml volumetric flask, add 2 ml of dilute nitric acid (two percent v/v) and one ml of potassium dichromate solution (one percent, m/m). One ml of this solution is equivalent of 0.1 g of mercury. A-5.2.2 Stannous Chloride Solution -- Take 50 g of stannous chloride in a beaker, add 25 ml of concentrated hydrochloric acid and boil for about 30 minutes and cool to room temperature. Add 225 ml of water. The solution should be clear. Transfer the solution to 250 ml bottle, add tin pellets and stopper. A-5.2.3 Sodium Hydroxide Solution -- 20 percent ( m/v). A-5.2.4 Dilute Sulphuric Acid-- (1 : 1). A-5.2.5 Potassium Permanganate Solution -- 1 percent ( m/v). A-5.2.6 Dilute Nitric Acid-- 10 percent ( v/v). A-5.3 Procedure A-5.3.1 Prepare a solution of the material as prescribed in A 4.3.1. A-5.3.2 Determine the mercury content with the cold vapour atomic absorptiometer in accordance with the manufacturers' directions.

A-6. DETERMINATION OF HEAVY METALS
A-6.1 Prepare a solution of the material as in A-4.3.1 and determine the heavy metals as prescribed in IS : 7017-1973*. A-7. TEST FOR SODIUM FORMATE A-7.1 Reagents A-7.1.1 Sodium Hydroxide -- 30 percent. A-7.1.2 Hydrogen Peroxide-- 5 percent. A-7.1.3 Dilute Potassium Bromate -- 0.1 N. A-7.1.4 Potassium Bromide-- solid. A-7.1.5 Potassium Iodide -- solid.
*Method for colorimetric determination of heavy metals by dithizone.

12

IS : 1919 - 1982 A-7.1.6 Standard Sodium Thiosulphate Solution -- 0.1 N. A-7.1.7 Starch Solution A-7.2 Procedure -- Accurately weigh 3 g of sample with a chemical balance. Put the sample and dissolve in a round-bottom 300 ml acetylation flask in which 50 ml of water and 5 ml of 30 percent NaOH have been placed. Slowly add 50 ml of 5 percent H2O2. Slowly boil for about 30 to 60 minutes on direct fire, and oxidize until all sulphur compounds are converted to sulphate. Concentrate the solution to about 25-30 ml in order to decompose surplus H2O2. After cooling to normal temperature, add accurately 5 ml of 0.000 5 percent phenolphthalein solution with a whole pipette, and neutralize with 20 percent HC1. Next, add 30 ml of 0.1 N KBrO3 with a whole pipette, and further add 4 g of KBr and 20 ml of H2O. Then add 12 ml of 2N CH3COONa and 5 ml of 20 percent HC1, immediately connect the flask to a cooling tube, and allow the contents to react for one hour in a water bath of 60°C. (Use a cooling tube of 1 m long with a diameter of 9 mm provided with a universal joint.) After completing the reaction, take the flask out of hot bath, and cool for about 5 minutes in ice-water. While keeping the flask in ice-water, add one g of KL dissolved in 5 ml of H2O. Add 5 ml of water and 5 ml of 20 percent HC1. Then wash the inside of the cooling tube with 10 ml of water. After 5 minutes, take the flask out of the ice-water. Remove the cooling tube, and wash the joint with water and put the washings into the flask. Do not let washings spill out of the flask. Stopper the flask tightly. Next, titrate with 0.1 N Na2S2O3 solution. Add starch indicator when the solution turns to pale yellow and continue the titration until the blue colour disappears. In the blank test, put 5 ml of 30 percent NaOH into a round-bottomed 300 ml acetylation flask, and then add 5 ml of 0.000 5 percent phenolphthalein solution. Nautralize with 20 percent HC1. Add 20 ml of H2O and 30 ml of 0.1 N KBrO3 with a whole pipette. Further, add 4 g of KBR and 20 ml of water, and promptly connect the flask to the cooling tube. Carry out further procedures in the same manner. A-7.2.1 Reaction Equation KBrO3 + 5 Br + 6HCl = 6KC1 + 3H2O + 3Br2 3HCOONa + 3 HCl = 3HCOOH + 3NaCl 3HCOOH + 3Br2 = 6HBr + 3CO2 KBrO3 + 5 Br + 9HC1 + 3HCOONa = 6KC1 + 3H2O + 3NaCl + 6HBr + 3CO2 13

NOTE -- In this analytical operation, stopper the flask immediately after adding the reagents, in order to prevent the escape of Br2 gas.

IS : 1919 - 1982 A-7.2.2 Calculation Sodium formate, percent by mass = where A = volume of thio solution required for the blank, B = volume of thio required for the titration, C = normality of the thio solution, and D = mass in g of the material taken for test.

NOTE -- 1 ml of 0.1 N thio solution is equivalent to 0.003 4 g of sodium formate.

A-8. DETECTION AND ESTIMATION OF METHANOL A 8.0 Method -- Methanol being a highly poisonous substance, normally the same should not be present in this grade of sodium hydrosulphite. However, a very minute trace of it is not likely to do any harm, as the material itself is usually subjected to a processing after the addition of sodium hydrosulphite, although not in all cases. Therefore, it shall be sufficient if a colour test along with a control test is done and the sample should not give more than a very nominal increase in colour than the control. A-8.1 Apparatus A-8.1.1 Conical Flasks -- of 100 ml capacity. A-8.1.2 Centrifuge A-8.1.3 Test Tubes A-8.1.4 Graduated Pipette A-8.2 Reagents A-8.2.1 Potassium Permanganate Reagent -- 30 g of potassium permanganate is dissolved in 150 ml of phosphoric acid and the volume made up to 1 000 ml. A-8.2.2 Oxalic Acid Reagent-- 50 g of oxalic acid is dissolved in 550 ml of sulphuric acid and volume made up to 1 000 ml. Both the reagents shall be cooled to room temperature. A-8.2.3 Schiff's Reagent -- Two g of fuchsin (p-Rosaniline hydrochloride) is dissolved in about 600 ml of hot water. This is transferred to a two litre flask, which is kept in ice. Then 40 g of sodium sulphite (Na2SO3.7H2O) dissolved in ice cold water is added to the flask containing fuchsin solution. To this is added 24 ml of concentrated hydrochloric acid drop by drop mixing and shaking 14

IS : 1919 - 1982 vigrorously; when a dark red to orange colour will be present. About two g of animal charcoal is added, shaken well and filtered. The filtrate is made up to two litres and kept in refrigerator in a properly closed glass bottle. It must be kept away from light and heat. A-8.3 Procedure -- Take 10.0 g of sodium hydrosulphite in a 100 ml conical flask and add 50 ml of absolute alcohol (ethyl), shake well and allow to settle. If a proper settlement does not happen, take a portion of the alcohol layer and centrifuge it. Use the clear solution for testing. A-8.3.1 Test in a Test-Tube -- Take 10 ml of the clear alcohol extract in test-tube and add about 5 ml of the potassium permanganate reagent. If the colour of KMnO4 does not persist add more, but note the quantity of KMnO4 reagent added totally. Keep the test-tube for about 15 to 20 minutes. Then add oxalic acid reagent slowly with stirring till the colour of KMnO4 is decolorized. (It is advisable to dip the test-tube in ice, while the addition of oxalic acid reagent is made, so that the reaction mixture is kept cool). When the decolorization has happened, add the cold Schiff's reagent (10 ml) along the sides of the test-tube without stirring and keep the test-tube without disturbing for about 30 to 45 minutes. Perform one control test also in another test-tube with all substances, except the extract of sodium hydrosulphite. The sodium hydrosulphite extract is to be replaced with the same amount of absolute alcohol, used in the extraction, that is 10 ml. A-8.3.2 Observation and Results -- If there is no methanol, no blue colour will be developed, but if any blue colour is developed, which will be from the top portion of the liquid to the bottom, the intensity of the colour shall not be more than a very meagre excess than the control. A-9. DETERMINATION OF SODIUM OXALATE A-9.1 Reagents A-9.1.1 Formaldehyde Solution -- 37 percent. A-9.1.2 Phenolphthalein Solution A-9.1.3 Dilute Sodium Hydroxide Solution -- 1 N. A-9.1.4 Glacial Acetic Acid A-9.1.5 Calcium Chloride Solution -- 5 percent. A-9.1.6 Dilute Acetic Acid Solution-- 5 percent ( v/v).

15

IS : 1919 - 1982 A-9.1.7 Neutral Formaldehyde Solution -- Take 50 ml formaldehyde solution (37 percent) in a beaker and add four drops of phenolphthalein indicator. To this add dropwise with stirring 1.0 N NaOH till it is faintly alkaline to phenolphthalein. Use this solution for dissolving sodium hydrosulphite. A-9.1.8 Dilute Solution of Neutral Formaldehyde -- Neutral formaldehyde made by the above procedure is used to make dilute formaldehyde solution. Take about 15 ml of neutral formaldehyde and about 40-45 ml of distilled water to get dilute formaldehyde solution. A-9.1.9 Calcium Chloride Solution -- About 5 g of calcium chloride is dissolved in 100 ml of water. Solution must be very clear, if not it is to be filtered. A-9.2 Apparatus A-9.2.1 Conical Flask 100 ml Capacity A-9.2.2 Volumetric Flask 100 ml Capacity A-9.2.3 Large Test Tubes -- 50 ml capacity. A-9.2.4 Pipettes A-9.2.5 Beakers A-9.3 Procedure -- Transfer 10 g of sodium hydrosulphite to a 100 ml conical flask containing 30 ml of netural formaldehyde solution and dissolve by swirling the conical flask gently. Dissolution can be made more quicker by adding small doses of dilute solution of formaldehyde along the sides of the flask and swirling. After all the hydrosulphite has been dissolved, keep the flask for about two to three minutes without disturbing. Make up the solution to 100 ml in a volumetric flask. While the volume is being made up, add a few drops of dilute acetic acid to discharge the colour of phenolphthalein. A-9.3.1 Take 25 ml of this solution in a large test tube and add about 1.0 ml of glacial acetic acid, mix and then add about 10 ml of 5 percent calcium chloride solution, which is free from any turbidity and warm the test tube and keep. A-9.3.2 A control test is also to be carried out along with, which will contain 30 ml netural formaldehyde solution, an equivalent amount of dilute formaldehyde solution added to the sample, acetic acid; and also calcium chloride solution. A-9.3.3 Keep both the test tubes for about 15 minutes and observe whether any turbidity is produced. Any turbidity that may be produced in the test sample should not be a very meagre excess that might be produced in the control test, for the sample to pass test. 16

IS : 1919 - 1982 ( Clause 6.1 ) SAMPLING OF SODIUM HYDROSULPHITE B-1. GENERAL REQUIREMENTS OF SAMPLING B-1.0 In drawing, preparing, storing and handling samples, the following precautions and directions shall be observed. B-1.1 Samples shall not be taken in an exposed place. B-1.2 The sampling instrument shall be clean and dry when used. B-1.3 Precautions shall be taken to protect the samples, the material being sampled, the sampling instrument and the containers for samples from adventitious contamination, particularly from absorption of moisture and acid fumes. B-1.4 The samples shall be placed in suitable, clean, dry and air-tight glass or any other containers on which the material has no action. B-1.5 The sample containers shall be of such a size that they are at least three quarters filled with the sample. B-1.6 Each sample container shall be sealed air-tight with a suitable stopper after filling, and marked with full details of the material (see 5.2) and the date of sampling. B-1.7 Samples shall be stored in a cool and dry place. B-2. SCALE OF SAMPLING B-2.1 Lot -- All the containers in a single consignment of the material drawn from a single batch of manufacture shall constitute a lot. If a consignment is declared or known to consist of different batches of manufacture, the batches shall be marked separately and the groups of containers in each batch shall constitute separate lots. B-2.2 For ascertaining the conformity of the material to the requirements of the specification, samples shall be selected and tested for each lot separately. B-2.3 The number of containers to be selected from a lot shall depend upon the size of the lot and shall be in accordance with Table 2. 17

APPENDIX

B

IS : 1919 - 1982
TABLE 2 SCALE OF SAMPLING ( Clause B-2.3 )
LOT SIZE

N

SAMPLE SIZE

n

(1) 3 to 15 16 to 40 41 to 65 66 to 110 111 and above

(2) 3 4 5 7 10

B-2.3.1 The containers shall be selected at random. In order to ensure the randomness of selection, procedures given in IS : 4905-1968* may be used.

B-3. PREPARATION OF TEST SAMPLES

B-3.0 Commercial hydrosulphite powders are usually quite heterogeneous and contain components which tend to segregate because of different crystal sizes. Lack of proper attention, while taking sample, may result in assay errors of as much as 4 percent. Consequently, it is desirable to pay close attention to the instructions given in B-3.1.1 and B-3.1.2, in taking samples for analysis. B-3.1 From each of the containers selected according to B-2.3, a representative sample of 200 g shall be taken with the help of the sampler given in B-3.1.1. Each of these samples shall constitute individual test sample. This shall be divided into three equal parts and each shall be transferred to a thoroughly dried bottle which shall be suitably secured against contamination. These bottles shall be labelled with all the particulars of the sampling given in B-1.6. One set of individual test samples shall be sent to the purchaser and one to the supplier, and the third set bearing the seals of purchaser and the supplier shall constitute a referee sample to be used in the case of dispute between the two. B-3.1.1 A suitable sampler is to be used for taking a representative sample of sodium hydrosulphite (see Fig. 2). This sampler consists of two long concentric cylinders with handle and screw cap at each end. The outer cylinder will have to two notches for locking the inner one in position. Both the cylinders have a series of holes; which can coincide as well as close depending upon the manipulation done with the handle.
*Methods for random sampling.

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IS : 1919 - 1982 Handle is put on the top and screw cap at the bottom. To take sample from the hydrosulphite drum, the sampler is pushed into the body of hydrosulphlte. While pushing the sampler, the holes are not in the coinciding positions. When the sampler has reached almost the bottom of the drum, the handle is turned in for the holes in the internal and external cylinders to coincide. By giving a light jerk hydrosulphlte from different layers of drum enter the sampler. The holes are closed again by turning the handle. Take the sampler out of the drum. Then the bottom screw is unscrewed and the hydrosulphlte is discharged into a sampler bottle. Mix the sample well with a spatula and keep the bottle closed. The capacity of the bottle must be such that, the sample material fills almost three fourth of the bottle capacity, to avoid too much air coming in contact with a small quantity of the sample. This mixed sample is ready for analysis. B-3.1.2 The portion taken for analysis shall not be removed by pouring from the bottle, but with a spatula or by holding the sample bottle at a slight incline and pushing a weighing bottle into hydrosulphlte until the weighing bottle is filled to the desired level. Pouring the sample from the bottle will have non-respresentative results because the portion thus secured for analysis will contain a disproportionately large amount of the bigger granules of varying strength. B-4. NUMBER OF TESTS AND CRITERIA FOR CONFORMITY B-4.1 Tests for the determination of sodium hydrosulphite bulk density, zinc mercury and heavy metals shall be performed on each of the individual test samples. B-4.2 From the individual test results obtained for the selected containers, the mean ( ) and range (R) shall be calculated separately for the sodium hydrosulphite content, bulk density zinc, mercury and heavy metals (range being defined as the difference between the maximum and the minimum of individual test results). The conformity of the lot to the requirements of the specification for the characteristics shall then be determined as follows: Characteristic Sodium hydrosulphite, percent by mass Bulk density, zinc, mercury and heavy metals Criteria for Conformity = - 0.6 R shall be greater than or equal to 84.0 for Grade 2 and 88.0 for Grade 1. = - 0.6 R shall be greater than or equal to 1.1, and = . + 0.6 R shall be less than or equal to 1.3. 19

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